OBJECTIVE To examine the degenerative effects that prolonged elevation of intraocular pressure has on retinal ganglion cell morphology RESULTS In glaucoma, retinal ganglion cells undergo a pattern of degeneration that originates with the dendritic arbor and ends with shrinkage of the cell body. DISCUSSION The monkey model of glaucoma was combined with intracellular staining techniques using an isolated retina preparation. Midget and parasol cells from normal and glaucomatous eyes were labelled intracellularly and their axons, somas and dendritic fields were compared using confocal microscopy. In midget and parasol cells, the earliest signs of pressure-induced degeneration involved structural abnormalities associated with the denritic arbor. Reduction in axon thickness appeared later. Chronic elevation of IOP resulted in significant decreases in the mean soma sizes of midget and parasol cells. Comparisons of eyes with different levels of optic nerve damage showed the axons and dentritic fields of parasol cells were significantly smaller at lower cup to disc ratios than were those of midget cells suggesting a differential effect. FUTURE DIRECTIONS The lateral geniculate nucleus and visual cortex from these same animals are under study, to determine the effects of elevated IOP and retinal ganglion cell death on these regions of the brain. Attempts will be made to intervene in early functional deficits and atrophy with neuroprotective agents or gene therapy. KEY WORDS neuroprotection, intraocular pressure, retina, degeneration FUNDING Alcon Laboratories, AHAF, NEI EY11159, NEI EY02698 PUBLICATIONS Weber AJ, Kaufman PL, Hubbard WC Morphology of single ganglion cells in the glaucomatous primate retina. Invest Ophthalmol Vis Sci. 39:2304-2320, 1998. [J]